ATF3 promotes erastin-induced ferroptosis by suppressing system Xc

Role of glutamine and its metabolite ammonia in crosstalk of cancer-associated fibroblasts and cancer cells

Cancer-associated fibroblasts (CAFs), the most abundant cells in the tumor microenvironment, play an indispensable role in cancer initiation, progression, metastasis, and metabolism. The limitations of traditional treatments can be partly attributed to the lack of understanding of the role of the tumor stroma. For this reason, CAF targeting is gradually gaining attention, and many studies are trying to overcome the limitations of tumor treatment with CAF as a breakthrough. Glutamine (GLN) has been called a “nitrogen reservoir” for cancer cells because of its role in supporting anabolic processes such as fuel proliferation and nucleotide synthesis, but ammonia is a byproduct of the metabolism of GLN and other nitrogenous compounds. Moreover, in some studies, GLN has been reported as a fundamental nitrogen source that can support tumor biomass. In this review, we discuss the latest findings on the role of GLN and ammonia in the crosstalk between CAFs and cancer cells as well as the potential therapeutic implications of nitrogen metabolism.

A ferroptosis-associated gene signature for the prediction of prognosis and therapeutic response in luminal-type breast carcinoma

Ferroptosis is a new form of regulated cell death (RCD), and its emergence has provided a new approach to the progression and drug resistance of breast cancer (BRCA). However, there is still a great gap in the study of ferroptosis-related genes in BRCA, especially luminal-type BRCA patients. We downloaded the mRNA expression profiles and corresponding clinical data of BRCA patients from the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) and The Cancer Genome Atlas (TCGA) databases. Then, we built a prognostic multigene signature with ferroptosis-related differentially expressed genes (DEGs) in the METABRIC cohort and validated it in the TCGA cohort. The predictive value of this signature was investigated in terms of the immune microenvironment and the probability of a response to immunotherapy and chemotherapy. The patients were divided into a high-risk group and a low-risk group according to the ferroptosis-associated gene signature, and the high-risk group had a worse overall survival (OS). The risk score based on the 10 ferroptosis-related gene-based signature was determined to be an independent prognostic predictor in both the METABRIC and TCGA cohorts (HR, 1.41, 95% CI, 1.14-1.76, P = 0.002; HR, 2.19, 95% CI, 1.13-4.26, P = 0.02). Gene set enrichment analysis indicated that the term "cytokine-cytokine receptor interaction" was enriched in the high-risk score subgroup. Moreover, the immune infiltration scores of most immune cells were significantly different between the two groups, the low-risk group was much more sensitive to immunotherapy, and six drugs might have potential therapeutic implications in the high-risk group. Finally, a nomogram incorporating a classifier based on the 10 ferroptosis-related genes, tumor stage, age and histologic grade was established. This nomogram showed favorable discriminative ability and could help guide clinical decision-making for luminal-type breast carcinoma.

Localized disruption of redox homeostasis boosting ferroptosis of tumor by hydrogel delivery system

Ferroptosis has received ever-increasing attention due to its unparalleled mechanism in eliminating resistant tumor cells. Nevertheless, the accumulation of toxic lipid peroxides (LPOs) at the tumor site is limited by the level of lipid oxidation. Herein, by leveraging versatile sodium alginate (ALG) hydrogel, a localized ferroptosis trigger consisting of gambogic acid (GA), 2,2'-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (AIPH), and Ink (a photothermal agent), was constructed via simple intratumor injection. Upon 1064 ​nm laser irradiation, the stored AIPH rapidly decomposed into alkyl radicals (R•), which aggravated LPOs in tumor cells. Meanwhile, GA could inhibit heat shock protein 90 (HSP90) to reduce the heat resistance of tumor cells, and forcefully consume glutathione (GSH) to weaken the antioxidant capacity of cells. Systematic in vitro and in vivo experiments have demonstrated that synchronous consumption of GSH and increased reactive oxygen species (ROS) facilitated reduced expression of glutathione peroxidase 4 (GPX4), which further contributed to disruption of intracellular redox homeostasis and ultimately boosted ferroptosis. This all-in-one strategy has a highly effective tumor suppression effect by depleting and generating fatal active compounds at tumor sites, which would pave a new route for the controllable, accurate, and coordinated tumor treatments.

Ferroptosis and its emerging role in tumor

Ferroptosis is a novel form of programmed cell death characterized by iron-dependent lipid peroxidation accumulation. It is morphologically, biochemically, and genetically distinct from other known cell death, such as apoptosis, necrosis, and pyroptosis. Its regulatory mechanisms include iron metabolism, fatty acid metabolism, mitochondrial respiration, and antioxidative systems eliminating lipid peroxidation, such as glutathione synthesis, selenium-dependent glutathione peroxidase 4, and ubiquinone. The disruption of cellular redox systems causes damage to the cellular membrane leading to ferroptotic cell death. Recent studies have shown that numerous pathological diseases, like tumors, neurodegenerative disorders, and ischemia-reperfusion injury are associated with ferroptosis. As such, pharmacological regulation of ferroptosis either by activation or by suppression will provide a vast potential for treatments of relevant diseases. This review will discuss the advanced progress in ferroptosis and its regulatory mechanisms from both the antioxidative and oxidative sides. In addition, the roles of ferroptosis in various tumorigenesis, development, and therapeutic strategies will be addressed, particularly to chemotherapy and immunotherapy, as well as the discoveries from Traditional Chinese Medicine. This review will lead us to have a comprehensive understanding of the future exploration of ferroptosis and cancer therapy.

Recent advances in cancer immunotherapy

Cancer immunotherapy represents a major advance in the cure of cancer following the dramatic advancements in the development and refinement of chemotherapies and radiotherapies. In the recent decades, together with the development of early diagnostic techniques, immunotherapy has significantly contributed to improving the survival of cancer patients. The immune-checkpoint blockade agents have been proven effective in a significant fraction of standard therapy refractory patients. Importantly, recent advances are providing alternative immunotherapeutic tools that could help overcome their limitations. In this mini review, we provide an overview on the main steps of the discovery of classic immune-checkpoint blockade agents and summarise the most recent development of novel immunotherapeutic strategies, such as tumour antigens, bispecific antibodies and TCR-engineered T cells.

Engineering nanomedicine for glutathione depletion-augmented cancer therapy

Glutathione (GSH), the main redox buffer, has long been recognized as a pivotal modulator of tumor initiation, progression and metastasis. It is also implicated in the resistance of platinum-based chemotherapy and radiation therapy. Therefore, depleting intracellular GSH was considered a potent solution to combating cancer. However, reducing GSH within cancer cells alone always failed to yield desirable therapeutic effects. In this regard, the convergence of GSH-scavenging agents with therapeutic drugs has thus been pursued in clinical practice. Unfortunately, the therapeutic outcomes are still unsatisfactory due to untargeted drug delivery. Advanced nanomedicine of synergistic GSH depletion and cancer treatment has attracted tremendous interest because they promise to deliver superior therapeutic benefits while alleviating life-threatening side effects. In the past five years, the authors and others have demonstrated that numerous nanomedicines, by simultaneously delivering GSH-depleting agents and therapeutic components, boost not only traditional chemotherapy and radiotherapy but also multifarious emerging treatment modalities, including photodynamic therapy, sonodynamic therapy, chemodynamic therapy, ferroptosis, and immunotherapy, to name a few, and achieved decent treatment outcomes in a large number of rodent tumor models. In this review, we summarize the most recent progress in engineering nanomedicine for GSH depletion-enhanced cancer therapies. Biosynthesis of GSH and various types of GSH-consuming strategies will be briefly introduced. The challenges and perspectives of leveraging nanomedicine for GSH consumption-augmented cancer therapies will be discussed at the end.

Ferroptosis: the potential value target in atherosclerosis

In advanced atherosclerosis (AS), defective function-induced cell death leads to the formation of the characteristic necrotic core and vulnerable plaque. The forms and mechanisms of cell death in AS have recently been elucidated. Among them, ferroptosis, an iron-dependent form of necrosis that is characterized by oxidative damage to phospholipids, promotes AS by accelerating endothelial dysfunction in lipid peroxidation. Moreover, disordered intracellular iron causes damage to macrophages, vascular smooth muscle cells (VSMCs), vascular endothelial cells (VECs), and affects many risk factors or pathologic processes of AS such as disturbances in lipid peroxidation, oxidative stress, inflammation, and dyslipidemia. However, the mechanisms through which ferroptosis initiates the development and progression of AS have not been established. This review explains the possible correlations between AS and ferroptosis, and provides a reliable theoretical basis for future studies on its mechanism.

Understanding p53 tumour suppressor network

The mutation of TP53 gene affects half of all human cancers, resulting in impairment of the regulation of several cellular functions, including cell cycle progression and cell death in response to genotoxic stress. In the recent years additional p53-mediated tumour suppression mechanisms have been described, questioning the contribution of its canonical pathway for tumour suppression. These include regulation of alternative cell death modalities (i.e. ferroptosis), cell metabolism and the emerging role in RNA stability. Here we briefly summarize our knowledge on p53 “canonical DNA damage response” and discuss the most relevant recent findings describing potential mechanistic explanation of p53-mediated tumour suppression.

System Xc-: a key regulatory target of ferroptosis in cancer

Ferroptosis is a type of oxidative stress-dependent regulated necrosis characterized by excessive lipid peroxide accumulation. This novel cell death modality has been implicated in preventing cancer progression. Cancer cells tend to modulate their redox state to prevent excessive peroxidation, eventually facilitating tumor growth. System Xc^- (a cystine/glutamate antiporter system) is a promising target in cancer cells for ferroptosis induction. The overexpression of system Xc^-, especially its core subunit xCT, has been reported in several tumors, and these high expression levels were closely related to cancer cell proliferation, invasion, metastasis and the tumor microenvironment. xCT might serve as a novel biomarker, and its upregulation almost always indicates drug tolerance and poor survival. Therefore, system Xc^- inhibition may enhance chemotherapy sensitivity and optimize patient prognosis. Here, we elaborate on the mediation of ferroptosis by suppressing system Xc^- and the relevant underlying molecular mechanism in cancer cells. The spotlight on this approach to cancer treatment is creating a new horizon and pointing to future opportunities.

Targeting iron metabolism in cancer therapy

Iron is a critical component of many cellular functions including DNA replication and repair, and it is essential for cell vitality. As an essential element, iron is critical for maintaining human health. However, excess iron can be highly toxic, resulting in oxidative DNA damage. Many studies have observed significant associations between iron and cancer, and the association appears to be more than just coincidental. The chief characteristic of cancers, hyper-proliferation, makes them even more dependent on iron than normal cells. Cancer therapeutics are becoming as diverse as the disease itself. Targeting iron metabolism in cancer cells is an emerging, formidable field of therapeutics. It is a strategy that is highly diverse with regard to specific targets and the various ways to reach them. This review will discuss the importance of iron metabolism in cancer and highlight the ways in which it is being explored as the medicine of tomorrow.

Ferroptosis and Its Potential Role in Metabolic Diseases: A Curse or Revitalization?

Ferroptosis is classified as an iron-dependent form of regulated cell death (RCD) attributed to the accumulation of lipid hydroperoxides and redox imbalance. In recent years, accumulating researches have suggested that ferroptosis may play a vital role in the development of diverse metabolic diseases, for example, diabetes and its complications (e.g., diabetic nephropathy, diabetic cardiomyopathy, diabetic myocardial ischemia/reperfusion injury and atherosclerosis [AS]), metabolic bone disease and adrenal injury. However, the specific physiopathological mechanism and precise therapeutic effect is still not clear. In this review, we summarized recent advances about the development of ferroptosis, focused on its potential character as the therapeutic target in metabolic diseases, and put forward our insights on this topic, largely to offer some help to forecast further directions.

A Ferroptosis-Related Gene Signature Identified as a Novel Prognostic Biomarker for Colon Cancer

Background

Colon cancer (CC) is a common gastrointestinal malignant tumor with high heterogeneity in clinical behavior and response to treatment, making individualized survival prediction challenging. Ferroptosis is a newly discovered iron-dependent cell death that plays a critical role in cancer biology. Therefore, identifying a prognostic biomarker with ferroptosis-related genes provides a new strategy to guide precise clinical decision-making in CC patients.

Methods

Alteration in the expression profile of ferroptosis-related genes was initially screened in GSE39582 dataset involving 585 CC patients. Univariate Cox regression analysis and LASSO-penalized Cox regression analysis were combined to further identify a novel ferroptosis-related gene signature for overall survival prediction. The prognostic performance of the signature was validated in the GSE17536 dataset by Kaplan-Meier survival curve and time-dependent ROC curve analyses. Functional annotation of the signature was explored by integrating GO and KEGG enrichment analysis, GSEA analysis and ssGSEA analysis. Furthermore, an outcome risk nomogram was constructed considering both the gene signature and the clinicopathological features.

Results

The prognostic signature biomarker composed of 9 ferroptosis-related genes accurately discriminated high-risk and low-risk patients with CC in both the training and validation datasets. The signature was tightly linked to clinicopathological features and possessed powerful predictive ability for distinct clinical subgroups. Furthermore, the risk score was confirmed to be an independent prognostic factor for CC patients by multivariate Cox regression analysis (p < 0.05). Functional annotation analyses showed that the prognostic signature was closely correlated with pivotal cancer hallmarks, particularly cell cycle, transcriptional regulation, and immune-related functions. Moreover, a nomogram with the signature was also built to quantify outcome risk for each patient.

Conclusion

The novel ferroptosis-related gene signature biomarker can be utilized for predicting individualized prognosis, optimizing survival risk assessment and facilitating personalized management of CC patients.

Development and Validation of a Random Forest Diagnostic Model of Acute Myocardial Infarction Based on Ferroptosis-Related Genes in Circulating Endothelial Cells

The high incidence and mortality of acute myocardial infarction (MI) drastically threaten human life and health. In the past few decades, the rise of reperfusion therapy has significantly reduced the mortality rate, but the MI diagnosis is still by means of the identification of myocardial injury markers without highly specific biomarkers of microcirculation disorders. Ferroptosis is a novel reported type of programmed cell death, which plays an important role in cancer development. Maintaining iron homeostasis in cells is essential for heart function, and its role in the pathological process of ischemic organ damages remains unclear. Being quickly detected through blood tests, circulating endothelial cells (CECs) have the potential for early judgment of early microcirculation disorders. In order to explore the role of ferroptosis-related genes in the early diagnosis of acute MI, we relied on two data sets from the GEO database to first detect eight ferroptosis-related genes differentially expressed in CECs between the MI and healthy groups in this study. After comparing different supervised learning algorithms, we constructed a random forest diagnosis model for acute MI based on these ferroptosis-related genes with a compelling diagnostic performance in both the validation (AUC = 0.8550) and test set (AUC = 0.7308), respectively. These results suggest that the ferroptosis-related genes might play an important role in the early stage of MI and have the potential as specific diagnostic biomarkers for MI.

CIRBP promotes ferroptosis by interacting with ELAVL1 and activating ferritinophagy during renal ischaemia-reperfusion injury

Renal ischaemia-reperfusion (IR) is a major cause of acute kidney injury (AKI). Cold-inducible RNA-binding protein (CIRBP) may contribute to AKI because its deficiency protects against renal IR injury in a mechanism believed to involve ferroptosis. We aimed to investigate whether ferroptosis is associated with CIRBP-mediated renal damage. The differential expression of CIRBP was examined in tubular epithelial (HK2) cells during hypoxia-reoxygenation (HR) or in response to erastin, an inducer of ferroptosis. CIRBP expression was increased in response to HR or erastin in HK2 cells but the silencing of CIRBP inhibited HR and erastin-induced ferroptosis together with ferritinophagy. We discovered an interaction between CIRBP and ELAVL1 using STRING software, which was verified through co-immunoprecipitation and fluorescence colocalization assays. We found that ELAVL1 is a critical regulator in the activation of ferritinophagy and the promotion of ferroptosis. HR or erastin also induced the expression of ELAVL1. An autophagy inhibitor (hydroxychloroquine) or si-ELAVL1 transfection reversed CIRBP-enhanced ferritinophagy activation and ferroptosis in HK2 cells under HR. Injection of anti-CIRBP antibody into a mouse model of IR inhibited ferroptosis and decreased renal IR injury in vivo. In summary, our results provide evidence that ferritinophagy-mediated ferroptosis could be responsible for CIRBP-enhanced renal IR injury.

PARP inhibition promotes ferroptosis via repressing SLC7A11 and synergizes with ferroptosis inducers in BRCA-proficient ovarian cancer

Pharmacologic inhibition of PARP is the primary therapeutic strategy for BRCA mutant ovarian cancer. However, most of patients carry wild-type BRCA1/2 with no significant clinical benefits from PARP inhibitors, calling for the needs to further understanding and developing new strategy when employing PARP inhibitors to treat ovarian cancer. Here, we show that ferroptosis, a form of regulated cell death driven by iron-dependent phospholipid peroxidation, is partly responsible for the efficacy of PARP inhibitor olaparib. Mechanistically, pharmacological inhibition or genetic deletion of PARP downregulates the expression of cystine transporter SLC7A11 in a p53-dependent manner. Consequently, decreased glutathione biosynthesis caused by SLC7A11 repression promotes lipid peroxidation and ferroptosis. Furthermore, ferroptosis perturbation results in significant resistance to olaparib without affecting DNA damage response, while boosting ferroptosis by ferroptosis inducers (FINs) synergistically sensitizes BRCA-proficient ovarian cancer cells and xenografts to PARP inhibitor. Together, our results reveal a previously unappreciated mechanism coupling ferroptosis to PARP inhibition and suggest the combination of PARP inhibitor and FINs in the treatment of BRCA-proficient ovarian cancer.

Lipoxin A4 protects primary spinal cord neurons from Erastin-induced ferroptosis by activating the Akt/Nrf2/HO-1 signaling pathway

Ferroptosis is an iron‐dependent programmed cell death, which participates in the pathogenesis of spinal cord injury (SCI). Our previous study has revealed that Lipoxin A4 (LXA4) exerts a protective role in SCI. Here, we investigated whether LXA4 can protect SCI through inhibiting neuronal ferroptosis. We treated primary spinal cord neurons with Erastin (ferroptosis activator) to induce ferroptosis. Erastin treatment reduced cell viability and enhanced cell death of primary spinal cord neurons, which was rescued by ferrostatin‐1 (ferroptosis inhibitor). Moreover, Erastin repressed glutathione peroxidase 4 (GPX4) expression and the levels of glutathione and cysteine in primary spinal cord neurons. Erastin also enhanced the expression of ferroptosis biomarkers (PTGS2 and ACSL4) and the levels of reactive oxygen species (ROS) in primary spinal cord neurons. The influence conferred by Erastin was effectively abolished by LXA4 treatment. Furthermore, LXA4 enhanced the protein expression of p‐AKT, nuclear factor (erythroid‐derived 2)‐like 2 (Nrf2) and haem‐oxygenase‐1 (HO‐1) in primary spinal cord neurons. LXA4‐mediated inhibition of ferroptosis of primary spinal cord neurons was prohibited by LY294002 (AKT inhibitor), brusatol (Nrf2 inhibitor) or zinc protoporphyrin (HO‐1 inhibitor). In conclusion, this work demonstrated that LXA4 exerted a neuroprotective effect in Erastin‐induced ferroptosis of primary spinal cord neurons by activating the Akt/Nrf2/HO‐1 signaling pathway. Thus, this work provides novel insights into the mechanisms of action of LXA4 in ferroptosis of primary spinal cord neurons and indicates that LXA4 may be a potential therapeutic agent for SCI.

Mechanisms of Regulated Cell Death: Current Perspectives

Balancing cell survival and cell death is fundamental to development and homeostasis. Cell death is regulated by multiple interconnected signaling pathways and molecular mechanisms. Regulated cell death (RCD) is implicated in fundamental processes such as organogenesis and tissue remodeling, removal of unnecessary structures or cells, and regulation of cell numbers. RCD can also be triggered by exogenous perturbations of the intracellular or extracellular microenvironment when the adaptive processes that respond to stress fail. During the past few years, many novel forms of non-apoptotic RCD have been identified, and the characterization of RCD mechanisms at a molecular level has deepened our understanding of diseases encountered in human and veterinary medicine. Given the complexity of these processes, it has become clear that the identification of RCD cannot be based simply on morphologic characteristics and that descriptive and diagnostic terms presently used by pathologists-such as individual cell apoptosis or necrosis-appear inadequate and possibly misleading. In this review, the current understanding of the molecular machinery of each type of non-apoptotic RCD mechanisms is outlined. Due to the continuous discovery of new mechanisms or nuances of previously described processes, the limitations of the terms apoptosis and necrosis to indicate microscopic findings are also reported. In addition, the need for a standard panel of biomarkers and functional tests to adequately characterize the underlying RCD and its role as a mechanism of disease is considered.

Ferroptosis as a mechanism to mediate p53 function in tumor radiosensitivity

Ferroptosis, a form of regulated cell death triggered by lipid peroxidation, was recently identified as an important mechanism in radiotherapy (RT)-mediated tumor suppression and radioresistance, although the exact genetic contexts in which to target ferroptosis in RT remains to be defined. p53 is the most commonly mutated gene in human cancers and a major effector to RT. Here, we identify ferroptosis as a critical mechanism to mediate p53 function in tumor radiosensitivity. Mechanistically, RT-mediated p53 activation antagonizes RT-induced SLC7A11 expression and represses glutathione synthesis, thereby promoting RT-induced lipid peroxidation and ferroptosis. p53 deficiency promotes radioresistance in cancer cells or tumors at least partly through SLC7A11-mediated ferroptosis inhibition. Ferroptosis inducers (FINs) that inhibit SLC7A11 exert significant radiosensitizing effects in tumor organoids and patient-derived xenografts with p53 mutation or deficiency. Finally, we show that RT-induced ferroptosis correlates with p53 activation and better clinical outcomes to RT in cancer patients. Together, our study uncovers a previously unappreciated role of ferroptosis in p53-mediated radiosensitization and suggest using FINs in combination with RT to treat p53-mutant cancers.

Ferroptosis, radiotherapy, and combination therapeutic strategies

Ferroptosis, an iron-dependent form of regulated cell death driven by peroxidative damages of polyunsaturated-fatty-acid-containing phospholipids in cellular membranes, has recently been revealed to play an important role in radiotherapy-induced cell death and tumor suppression, and to mediate the synergy between radiotherapy and immunotherapy. In this review, we summarize known as well as putative mechanisms underlying the crosstalk between radiotherapy and ferroptosis, discuss the interactions between ferroptosis and other forms of regulated cell death induced by radiotherapy, and explore combination therapeutic strategies targeting ferroptosis in radiotherapy and immunotherapy. This review will provide important frameworks for future investigations of ferroptosis in cancer therapy.

ATF3 Promotes Arsenic-Induced Apoptosis and Oppositely Regulates DR5 and Bcl-xL Expression in Human Bronchial Epithelial Cells

Arsenic is one of the most common environmental pollutants eliciting serious public health issues; however, it is also a well-recognized chemotherapeutic agent for acute promyelocytic leukemia. The association between arsenic exposure and lung diseases has been established, but underlying molecular mechanisms are poorly defined. Here we investigated the toxicology of arsenic in airway epithelium. Arsenic rapidly induced the activating transcription factor ATF3 expression through the JNK and p38 pathways. The ATF3-deficient BEAS-2B cells were relatively resistant to apoptosis upon arsenic exposure, indicating a facilitatory role of ATF3 in arsenic-induced apoptosis. We further showed that ATF3 oppositely regulated the transcription of death receptor (DR5) and Bcl2-like 1 (Bcl-xL) by directly binding to the promoter DR5 and Bcl-xL. Altogether, our findings establish ATF3 as a pro-apoptotic protein in arsenic-induced airway epithelial apoptosis through transcriptionally regulating DR5 and Bcl-xL, highlighting the potential of ATF3 as an early and sensitive biomarker for arsenic-caused lung injury.

Deubiquitinase USP35 modulates ferroptosis in lung cancer via targeting ferroportin

BACKGROUND

Ferroptosis is essential to regulate tumor growth and serves as a promising therapeutic target to lung cancer. Ubiquitin-specific protease 35 (USP35) belongs to the deubiquitinases family that is associated with cell proliferation and mitosis. In this research, we aim to elucidate the potential role and molecular basis of USP35 in lung cancer.

METHODS

Lung cancer cells were infected with lentiviral vectors to silence or overexpress USP35. Cell viability, colony formation, lipid reactive oxygen species production, intracellular iron metabolism, and other ferroptotic markers were detected. The role of USP35 on ferroptosis and tumor progression were also tested in mouse tumor xenograft models in vivo.

RESULTS

USP35 was abundant in human lung cancer tissues and cell lines. USP35 knockdown promoted ferroptosis, and inhibited cell growth, colony formation, and tumor progression in lung cancer cells. USP35 overexpression did not affect tumorigenesis and ferroptosis under basal conditions, but reduced erastin/RSL3-triggered iron disturbance and ferroptosis, thereby facilitating lung cancer cell growth and tumor progression. Further studies determined that USP35 directly interacted with ferroportin (FPN) and functioned as a deubiquitinase to maintain its protein stability. More importantly, we observed that USP35 knockdown sensitized lung cancer cells to cisplatin and paclitaxel chemotherapy.

CONCLUSION

USP35 modulates ferroptosis in lung cancer via targeting FPN, and it is a promising therapeutic target to lung cancer.

Emerging mechanisms and targeted therapy of ferroptosis in cancer

Ferroptosis is an iron- and lipid reactive oxygen species (ROS)-dependent form of programmed cell death that is distinct from other forms of regulatory cell death at the morphological, biological, and genetic levels. Emerging evidence suggests critical roles for ferroptosis in cell metabolism, the redox status, and various diseases, such as cancers, nervous system diseases, and ischemia-reperfusion injury, with ferroptosis-related proteins. Ferroptosis is inhibited in diverse cancer types and functions as a dynamic tumor suppressor in cancer development, indicating that the regulation of ferroptosis can be utilized as an interventional target for tumor treatment. Small molecules and nanomaterials that reprogram cancer cells to undergo ferroptosis are considered effective drugs for cancer therapy. Here, we systematically summarize the molecular basis of ferroptosis, the suppressive effect of ferroptosis on tumors, the effect of ferroptosis on cellular metabolism and the tumor microenvironment (TME), and ferroptosis-inducing agents for tumor therapeutics. An understanding of the latest progress in ferroptosis could provide references for proposing new potential targets for the treatment of cancers.

TRIM26 Induces Ferroptosis to Inhibit Hepatic Stellate Cell Activation and Mitigate Liver Fibrosis Through Mediating SLC7A11 Ubiquitination

Hepatic stellate cells (HSCs) are activated by inflammatory mediators to secrete extracellular matrix for collagen deposition, leading to liver fibrosis. Ferroptosis is iron- and lipid hydroperoxide-dependent programmed cell death, which has recently been targeted for inhibiting liver fibrogenic processes. Tripartite motif-containing protein 26 (TRIM26) is an E3 ubiquitin ligase that functions as a tumor suppressor in hepatocellular carcinoma, while little is known about its function in liver fibrosis. In the present study, the differential expression of TRIM26 in normal and fibrotic liver tissues was examined based on both online databases and specimens collected from patient cohort. The effects of TRIM26 on HSCs ferroptosis were examined in vitro through evaluating cell proliferation, lipid peroxidation, and expression of key ferroptosis-related factors. In vivo function of TRIM26 in liver fibrosis was examined based on CCl₄-induced mice model. We found that TRIM26 was downregulated in fibrotic liver tissues. The overexpression of TRIM26 inhibited HSCs proliferation, promoted lipid peroxidation, manipulated ferroptosis-related factor expressions, and counteracted the effect of iron inhibitor deferoxamine. Moreover, TRIM26 physically interacted with solute carrier family-7 member-11 (SLC7A11), a critical protein for lipid reactive oxygen species (ROS) scavenging, and mediated its ubiquitination. In addition, TRIM26 overexpression induced HSCs ferroptosis and mitigated CCl₄-induced liver fibrosis in mice. In conclusion, TRIM26 promotes HSCs ferroptosis to suppress liver fibrosis through mediating the ubiquitination of SLC7A11. The TRIM26-targeted SLC7A11 suppression can be a novel therapeutic strategy for liver fibrosis.

Endogenous glutamate determines ferroptosis sensitivity via ADCY10-dependent YAP suppression in lung adenocarcinoma

Rationale: Ferroptosis, a newly identified form of regulated cell death, can be induced following the inhibition of cystine-glutamate antiporter system X_C^- because of the impaired uptake of cystine. However, the outcome following the accumulation of endogenous glutamate in lung adenocarcinoma (LUAD) has not yet been determined. Yes-associated protein (YAP) is sustained by the hexosamine biosynthesis pathway (HBP)-dependent O-linked beta-N-acetylglucosaminylation (O-GlcNAcylation), and glutamine-fructose-6-phosphate transaminase (GFPT1), the rate-limiting enzyme of the HBP, can be phosphorylated and inhibited by adenylyl cyclase (ADCY)-mediated activation of protein kinase A (PKA). However, whether accumulated endogenous glutamate determines ferroptosis sensitivity by influencing the ADCY/PKA/HBP/YAP axis in LUAD cells is not understood.

Methods: Cell viability, cell death and the generation of lipid reactive oxygen species (ROS) and malondialdehyde (MDA) were measured to evaluate the responses to the induction of ferroptosis following the inhibition of system X_C^-. Tandem mass tags (TMTs) were employed to explore potential factors critical for the ferroptosis sensitivity of LUAD cells. Immunoblotting (IB) and quantitative RT-PCR (qPCR) were used to analyze protein and mRNA expression. Co-immunoprecipitation (co-IP) assays were performed to identify protein-protein interactions and posttranslational modifications. Metabolite levels were measured using the appropriate kits. Transcriptional regulation was evaluated using a luciferase reporter assay, chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift assay (EMSA). Drug administration and limiting dilution cell transplantation were performed with cell-derived xenograft (CDX) and patient-derived xenograft (PDX) mouse models. The associations among clinical outcome, drug efficacy and ADCY10 expression were determined based on data from patients who underwent curative surgery and evaluated with patient-derived primary LUAD cells and tissues.

Results: The accumulation of endogenous glutamate following system X_C^- inhibition has been shown to determine ferroptosis sensitivity by suppressing YAP in LUAD cells. YAP O-GlcNAcylation and expression cannot be sustained in LUAD cells upon impairment of GFPT1. Thus, Hippo pathway-like phosphorylation and ubiquitination of YAP are enhanced. ADCY10 acts as a key downstream target and diversifies the effects of glutamate on the PKA-dependent suppression of GFPT1. We also discovered that the protumorigenic and proferroptotic effects of ADCY10 are mediated separately. Advanced-stage LUADs with high ADCY10 expression are sensitive to ferroptosis. Moreover, LUAD cells with acquired therapy resistance are also prone to higher ADCY10 expression and are more likely to respond to ferroptosis. Finally, a varying degree of secondary labile iron increase is caused by the failure to sustain YAP-stimulated transcriptional compensation for ferritin at later stages further explains why ferroptosis sensitivity varies among LUAD cells.

Conclusions: Endogenous glutamate is critical for ferroptosis sensitivity following the inhibition of system X_C^- in LUAD cells, and ferroptosis-based treatment is a good choice for LUAD patients with later-stage and/or therapy-resistant tumors.

ATF3 Suppresses Growth and Metastasis of Clear Cell Renal Cell Carcinoma by Deactivating EGFR/AKT/GSK3β/β-Catenin Signaling Pathway

Background

Clear cell renal cell carcinoma (ccRCC) is one of the most common malignant cancers in East Asia, with high incidence and mortality. Accumulating evidence has shown that ATF3 is associated with tumor progression.

Methods

Using qPCR, the expression of ATF3 was detected in 93 patients with ccRCC, including 24 paired normal and tumor tissues, which were used to further compare ATF3 expression through western blotting and immunohistochemistry. Lentivirus was used for the overexpression or knockdown of ATF3, and the consequent alteration in function was analyzed through CCK8 assay, colony formation assay, wound healing assay, invasion assay, and flow cytometry. The potential mechanism affected by ATF3 was analyzed through gene set enrichment analysis (GSEA) and verified using western blotting, invasion assay, or immunofluorescence staining. Furthermore, a xenograft mouse model was used to assess the function of ATF3 in vivo.

Results

ATF3 expression was significantly decreased in ccRCC compared to that in adjacent normal tissues. Through gain- and loss-of-function experiments performed in an in vitro assay, we found that ATF3 could regulate ccRCC cell proliferation, cycle progression, migration, and invasion. In the in vivo study, the xenograft mouse model revealed that ATF3 overexpression can inhibit the growth of ccRCC. Moreover, the mechanism analysis showed that suppression of ATF3 could lead to an increase the expression of β-catenin and promote β-catenin transfer to the nucleus, and might be affected by EGFR/AKT/GSK3β signaling.

Conclusion

ATF3 could be utilized as an independent protective factor to inhibit the progression of ccRCC. Potential treatment strategies for ccRCC include targeting the ATF3/EGFR/AKT/GSK3β/β-catenin signaling pathway.

Carthamin yellow improves cerebral ischemia‑reperfusion injury by attenuating inflammation and ferroptosis in rats

Carthamin yellow (CY), a flavonoid compound extracted from safflower, has been reported to attenuate cardiac ischemia and reperfusion injury. However, whether CY could ameliorate ischemic stroke is not completely understood. In the present study, the preventive effects of CY on experimental ischemic stroke were investigated using middle cerebral artery occlusion (MCAO) model rats. Neurological scores, brain edema, infarct area and microtubule‑associated protein 2 (MAP‑2) immunoreactivity were assessed to evaluate the effects of CY on ischemic brain injury. The involvement of inflammation and ferroptosis were examined to investigate the mechanism underlying the effects of CY. The results demonstrated that 2‑week CY treatment attenuated the neurological deficit score, brain water content and infarct area, and increased MAP‑2 immunoreactivity in the cortex in MCAO model rats. CY administration also deactivated the cortex NF‑κB/NLR family pyrin domain containing 3 inflammasome signaling pathway, and decreased serum TNF‑α, IL‑1β and IL‑6 concentrations. Moreover, CY treatment inhibited Fe²⁺ and reactive oxygen species accumulation, and reversed acyl‑CoA synthetase long‑chain family member 4, transferrin receptor 1, glutathione peroxidase 4 and ferritin heavy chain 1 protein expression levels in the brain. The levels of glutathione, superoxide dismutase and malondialdehyde in the serum were also reversed by CY treatment. Collectively, the results of the present study demonstrated that CY protected rats against ischemic stroke, which was associated with mitigation of inflammation and ferroptosis.

Ferroptosis: A Novel Mechanism of Artemisinin and its Derivatives in Cancer Therapy

BACKGROUND

Artemisinin is a sesquiterpene lactone compound with a special peroxide bridge that is tightly linked to the cytotoxicity involved in fighting malaria and cancer. Artemisinin and its derivatives (ARTs) are considered to be potential anticancer drugs that promote cancer cell apoptosis, induce cell cycle arrest and autophagy, inhibit cancer cell invasion and migration. Additionally, ARTs significantly increase intracellular Reactive Oxygen Species (ROS) in cancer cells, which result in ferroptosis, a new form of cell death, depending on the ferritin concentration. Ferroptosis is regarded as a cancer suppressor and as well as considered a new mechanism for cancer therapy.

METHODS

The anticancer activities of ARTs and reference molecules were compared by literature search and analysis. The latest research progress on ferroptosis was described, with a special focus on the molecular mechanism of artemisinin-induced ferroptosis.

RESULTS

Artemisinin derivatives, artemisinin-derived dimers, hybrids and artemisinin-transferrin conjugates, could significantly improve anticancer activity, and their IC50 values are lower than those of reference molecules such as doxorubicin and paclitaxel. The biological activities of linkers in dimers and hybrids are important in the drug design processes. ARTs induce ferroptosis mainly by triggering intracellular ROS production, promoting the lysosomal degradation of ferritin and regulating the System Xc-/Gpx4 axis. Interestingly, ARTs also stimulate the feedback inhibition pathway.

CONCLUSION

Artemisinin and its derivatives could be used in the future as cancer therapies with broader applications due to their induction of ferroptosis. Meanwhile, more attention should be paid to the development of novel artemisinin-related drugs based on the mechanism of artemisinininduced ferroptosis.

Quercetin alleviates acute kidney injury by inhibiting ferroptosis

INTRODUCTION

Ferroptosis is an iron-dependent regulated necrosis and has been proven to contribute to the progress of acute kidney injury (AKI). Quercetin (QCT), a natural flavonoid which is commonly found in numerous fruits and vegetables, has extensive pharmacological effects, such as anti-oxidant, anti-inflammatory and anti-senescence effects.

OBJECTIVES

This study aims to explain whether ferroptosis is a therapeutic strategy to AKI, and to explore the effect of QCT on AKI ferroptosis.

METHODS

NRK-52E cells and HK-2 cells were used for in vitro ferroptosis studies. Morphology of cells was detected by transmission electron microscopy. Lipid ROS was assayed using flow cytometry. In vivo, AKI was induced by ischemia-reperfusion (I/R) or folic acid (FA). To explore the molecular mechanisms, RNA-sequence analysis was performed. Transwell was used to detect macrophage migration.

RESULTS

We discovered that quercetin (QCT), a natural flavonoid, inhibited ferroptosis in renal proximal tubular epithelial cells. QCT blocked the typical morphologic changes of ferroptotic cells by reducing the levels of malondialdehyde (MDA) and lipid ROS and increasing the levels of glutathione (GSH). Moreover, QCT ameliorated AKI induced by I/R or FA. RNA-sequence analysis highlighted activation transcription factor 3 (ATF3), as it was the dominant one among all the 299 down-regulated genes by QCT. Knockdown of ATF3 could significantly increase the levels of SLC7A11, GPX4 and increased the cell viability. In addition, ferroptotic cells were found to be extremely pro-inflammatory by recruiting macrophages through CCL2, while QCT inhibited the chemotaxis of macrophages induced by ferroptosis in AKI.

CONCLUSIONS

Collectively, these results identify QCT as a ferroptosis inhibitor and provide new therapeutic strategies for diseases related to ferroptosis.

Ferroptosis: molecular mechanisms and health implications

Cell death can be executed through different subroutines. Since the description of ferroptosis as an iron-dependent form of non-apoptotic cell death in 2012, there has been mounting interest in the process and function of ferroptosis. Ferroptosis can occur through two major pathways, the extrinsic or transporter-dependent pathway and the intrinsic or enzyme-regulated pathway. Ferroptosis is caused by a redox imbalance between the production of oxidants and antioxidants, which is driven by the abnormal expression and activity of multiple redox-active enzymes that produce or detoxify free radicals and lipid oxidation products. Accordingly, ferroptosis is precisely regulated at multiple levels, including epigenetic, transcriptional, posttranscriptional and posttranslational layers. The transcription factor NFE2L2 plays a central role in upregulating anti-ferroptotic defense, whereas selective autophagy may promote ferroptotic death. Here, we review current knowledge on the integrated molecular machinery of ferroptosis and describe how dysregulated ferroptosis is involved in cancer, neurodegeneration, tissue injury, inflammation, and infection.

System Xc-: a key regulatory target of ferroptosis in cancer

Ferroptosis is a type of oxidative stress-dependent regulated necrosis characterized by excessive lipid peroxide accumulation. This novel cell death modality has been implicated in preventing cancer progression. Cancer cells tend to modulate their redox state to prevent excessive peroxidation, eventually facilitating tumor growth. System Xc^- (a cystine/glutamate antiporter system) is a promising target in cancer cells for ferroptosis induction. The overexpression of system Xc^-, especially its core subunit xCT, has been reported in several tumors, and these high expression levels were closely related to cancer cell proliferation, invasion, metastasis and the tumor microenvironment. xCT might serve as a novel biomarker, and its upregulation almost always indicates drug tolerance and poor survival. Therefore, system Xc^- inhibition may enhance chemotherapy sensitivity and optimize patient prognosis. Here, we elaborate on the mediation of ferroptosis by suppressing system Xc^- and the relevant underlying molecular mechanism in cancer cells. The spotlight on this approach to cancer treatment is creating a new horizon and pointing to future opportunities.

Metabolism of Amino Acids in Cancer

Metabolic reprogramming has been widely recognized as a hallmark of malignancy. The uptake and metabolism of amino acids are aberrantly upregulated in many cancers that display addiction to particular amino acids. Amino acids facilitate the survival and proliferation of cancer cells under genotoxic, oxidative, and nutritional stress. Thus, targeting amino acid metabolism is becoming a potential therapeutic strategy for cancer patients. In this review, we will systematically summarize the recent progress of amino acid metabolism in malignancy and discuss their interconnection with mammalian target of rapamycin complex 1 (mTORC1) signaling, epigenetic modification, tumor growth and immunity, and ferroptosis. Finally, we will highlight the potential therapeutic applications.

Juglone, a novel activator of ferroptosis, induces cell death in endometrial carcinoma Ishikawa cells

Ferroptosis is a novel iron-dependent cell death pathway mainly caused by an abnormal redox state and associated with various diseases including cancer. Recently, much attention has been paid to natural compounds that are involved in its activation and inhibition. This is the first ever study to demonstrate the role of juglone isolated from Carya cathayensis green peel in inducing autophagy and inhibiting endometrial cancer (EC) cell migration. Subsequently, Fe2+ accumulation, lipid peroxidation, GSH depletion, the upregulation of HMOX1, and heme degradation to Fe2+ were reported. Juglone was involved in inducing autophagy and inhibiting cell migration and endoplasmic reticulum stress, which are the new hallmarks of cancer treatment. Collectively, our data indicate that juglone as a functional food ingredient induces the programmed cell death of EC cells by activating oxidative stress and suggest a novel therapeutic approach for the treatment and prevention of EC.

Inhibition of ferroptosis by up-regulating Nrf2 delayed the progression of diabetic nephropathy

Diabetic nephropathy (DN) is now considered the leading cause of end-stage renal disease. In diabetes, the accumulation of reactive oxygen species (ROS) and iron overload are important determinants that promote the occurrence of DN. However, the underlying mechanism of how they cause diabetic kidney damage remains unclear. Ferroptosis, characterized by iron-dependent lipid peroxidation, provided us with a new idea to explore the progression of DN. Iron overload, reduced antioxidant capability, massive ROS and lipid peroxidation were detected in the kidneys of streptozotocin-induced DBA/2J diabetic mice and high-glucose cultured human renal proximal tubular (HK-2) cells, which were the symbolic changes of ferroptosis. Furthermore, the characteristic mitochondrial morphological changes of ferroptosis were observed in high glucose cultured cells. Additional treatment of Ferrostatin-1 (Fer-1) in DN models significantly rescued these changes and alleviated the renal pathological injuries in diabetic mice. Besides, the decreased NFE2-related factor 2 (Nrf2) was observed in DN models. The specific knockdown of Nrf2 increased the sensitivity of cells to ferroptosis in the high glucose condition. In Nrf2 knockdown cells, up-regulating Nrf2 by treating with fenofibrate improved the situation of ferroptosis, which was verified in RSL-3 induced cells. Moreover, the ferroptosis-related changes were inhibited by increasing Nrf2 in fenofibrate treated diabetic mice, which delayed the progression of DN. Collectively, we demonstrated that ferroptosis was involved in the development of DN, and up-regulating Nrf2 by treating with fenofibrate inhibited diabetes-related ferroptosis, delaying the progression of DN. Our research revealed the development mechanism of DN from a new perspective, and provide a new approach delaying the progression of DN.

Lipid Peroxidation, GSH Depletion, and SLC7A11 Inhibition Are Common Causes of EMT and Ferroptosis in A549 Cells, but Different in Specific Mechanisms

Epithelial-mesenchymal transition (EMT) induced by transforming growth factor-β1 (TGF-β1) is thought to be involved in the pathogenesis of pulmonary fibrosis. Emerging evidence suggested that there are some common causes between ferroptosis and pulmonary fibrosis. The interaction of EMT and ferroptosis and its mechanism were investigated by detecting the expression levels of α-smooth muscle actin (α-SMA), E-cadherin, solute carrier family 7 member 11 (SLC7A11), and glutathione peroxidase 4 (GPX4) and measuring the contents of reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione (GSH). The cellular morphology and ultrastructure of mitochondria were studied by microscope and transmission electron microscope (TEM), respectively. The results showed that ferroptosis in A549 cells was induced by Erastin, which decreased the expression levels of E-cadherin (E-Ca), α-SMA, and SLC7A11, accompanied with ROS and MDA increase, as well as GSH decrease. TGF-β1 promoted ultrastructure variation of mitochondria similar to ferroptosis and mesenchymal changes in morphology during EMT of A549 cells, accompanied with reduced GSH content and expression of SLC7A11, as well as ROS and MDA increase. Ferrostatin-1 (Fer-1) recovered ferroptosis induced by Erastin, but had no effect on the morphological change caused by TGF-β1. Furthermore, Fer-1 reduced ROS and MDA production, and increased SLC7A11 expression in the early subsequently increased GSH. However, the effects of Fer-1 on above indicators were different in time. The expression of GPX4 had no significant change during EMT induced by TGF-β1 and ferroptosis induced by Erastin in A549 cells. It is indicating that Erastin promoted the de-epithelialization of lung epithelial cells, but inhibited the process of myofibroblast differentiation; Fer-1 could partially inhibit EMT induced by TGF-β1, but reverse ferroptosis induced by Erastin. TGF-β1 could delay the ferroptosis, but could not prevent it. Lipid peroxidation, GSH depletion, and SLC7A11 inhibition are common causes of EMT and ferroptosis in A549 cells, but different in specific mechanisms. The exact effects of GPX4 involved in EMT and ferroptosis in A549 cells need further study.

The Molecular Mechanisms of Regulating Oxidative Stress-Induced Ferroptosis and Therapeutic Strategy in Tumors

Ferroptosis is an atypical form of regulated cell death, which is different from apoptosis, necrosis, pyroptosis, and autophagy. Ferroptosis is characterized by iron-dependent oxidative destruction of cellular membranes following the antioxidant system's failure. The sensitivity of ferroptosis is tightly regulated by a series of biological processes, the metabolism of iron, amino acids, and polyunsaturated fatty acids, and the interaction of glutathione (GSH), NADPH, coenzyme Q10 (CoQ10), and phospholipids. Elevated oxidative stress (ROS) level is a hallmark of cancer, and ferroptosis serves as a link between nutrition metabolism and redox biology. Targeting ferroptosis may be an effective and selective way for cancer therapy. The underlying molecular mechanism of ferroptosis occurrence is still not enough. This review will briefly summarize the process of ferroptosis and introduce critical molecules in the ferroptotic cascade. Furthermore, we reviewed the occurrence and regulation of reduction-oxidation (redox) for ferroptosis in cancer metabolism. The role of the tumor suppressor and the epigenetic regulator in tumor cell ferroptosis will also be described. Finally, old drugs that can be repurposed to induce ferroptosis will be characterized, aiming for drug repurposing and novel drug combinations for cancer therapy more efficiently and economically.

RRM2 protects against ferroptosis and is a tumor biomarker for liver cancer

Background

Ferroptosis is the process of cell death triggered by lipid peroxides, and inhibition of glutathione (GSH) synthesis leads to ferroptosis. Liver cancer progression is closely linked to ferroptosis suppression. However, the mechanism by which inhibition of GSH synthesis suppresses potential ferroptosis of liver cancer cells and whether ferroptosis-related liver cancer biomarkers have a promising diagnostic value remain unknown.

Methods

Ribonucleotide reductase regulatory subunit M2 (RRM2) levels were measured using an enzyme linked immunosorbent assay (ELISA), quantitative RT-PCR (qPCR), immunoblotting (IB) and immunochemistry (IHC). Cell viability and cell death were measured by a CellTiter-Glo luminescent cell viability assay and staining with SYTOX Green followed by flow cytometry, respectively. Metabolites were measured using the indicated kits. The Interaction between glutathione synthetase (GSS) and RRM2 was measured using immunofluorescence (IF), co-immunoprecipitation (co-IP) and the proximal ligation assay (PLA). The diagnostic value was analyzed using the area under the receiver operating characteristic curve (AUC-ROC). Bioinformatics analysis was performed using the indicated database.

Results

RRM2 showed specifically elevated levels in liver cancer and inhibited ferroptosis by stimulating GSH synthesis via GSS. Mechanistically, phosphorylation of RRM2 at the Threonine 33 residue (T33) was maintained at normal levels to block the RRM2–GSS interaction and therefore protected RRM2 and GSS from further proteasome degradation. However, under ferroptotic stress, RRM2 was dephosphorylated at T33, thus the RRM2–GSS interaction was promoted. This resulted in the translocation of RRM2 and GSS to the proteasome for simultaneous degradation. Clinically, serum RRM2 was significantly associated with serum alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma glutamyl transpeptidase (γ-GT), albumin (ALB) and total bilirubin. The AUC-ROC for the combination of RRM2 with AFP was 0.947, with a sensitivity of 88.7% and a specificity of 97.0%, which indicates better diagnostic performance compared to either RRM2 or AFP alone.

Conclusion

RRM2 exerts an anti-ferroptotic role in liver cancer cells by sustaining GSH synthesis. Serum RRM2 will be useful as a biomarker to evaluate the degree to which ferroptosis is suppressed and improve diagnostic efficiency for liver cancer.

The m6A reader YTHDC2 inhibits lung adenocarcinoma tumorigenesis by suppressing SLC7A11-dependent antioxidant function

The biological functions of N6-methyladenosine (m⁶A) RNA methylation are mainly dependent on the reader; however, its role in lung tumorigenesis remains unclear. Here, we have demonstrated that the m⁶A reader YT521-B homology domain containing 2 (YTHDC2) is frequently suppressed in lung adenocarcinoma (LUAD). Downregulation of YTHDC2 was associated with poor clinical outcome of LUAD. YTHDC2 decreased tumorigenesis in a spontaneous LUAD mouse model. Moreover, YTHDC2 exhibited antitumor activity in human LUAD cells. Mechanistically, YTHDC2, via its m⁶A-recognizing YTH domain, suppressed cystine uptake and blocked the downstream antioxidant program. Administration of cystine downstream antioxidants to pulmonary YTHDC2-overexpressing mice rescued lung tumorigenesis. Furthermore, solute carrier 7A11 (SLC7A11), the catalytic subunit of system X_C⁻, was identified to be the direct target of YTHDC2. YTHDC2 destabilized SLC7A11 mRNA in an m⁶A-dependent manner because YTHDC2 preferentially bound to m⁶A-modified SLC7A11 mRNA and thereafter promoted its decay. Clinically, a large proportion of acinar LUAD subtype cases exhibited simultaneous YTHDC2 downregulation and SLC7A11 elevation. Patient-derived xenograft (PDX) mouse models generated from acinar LUAD showed sensitivity to system X_C⁻ inhibitors. Collectively, the promotion of cystine uptake via the suppression of YTHDC2 is critical for LUAD tumorigenesis, and blocking this process may benefit future treatment.

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The m⁶A reader YTHDC2 is frequently suppressed in LUAD and indicates poor prognosis.

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YTHDC2 suppresses the antioxidant function of system X_C⁻ via its m⁶A reading domain.

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The mRNA encoding SLC7A11 is a direct target of YTHDC2.

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YTHDC2 preferentially accelerates the decay of m⁶A-methylated SLC7A11 mRNA.

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LUAD with YTHDC2 suppression is sensitive to system X_C⁻ inhibitors.

Research mechanisms of and pharmaceutical treatments for ferroptosis in liver diseases

Regulated cell death (RCD) is a universal process in living organisms that is essential for tissue homeostasis or to the restoration of biological equilibrium following stress. Ferroptosis is a specific nonapoptotic cell death that is dependent on iron and is very different from other forms of RCD. Ferroptosis can affect the development of liver diseases such as drug-induced liver injury (DILI), liver fibrosis, and hepatocellular carcinoma (HCC) by regulating the level of intracellular iron, the production of intracellular reactive oxygen species, and lipid peroxides. In this review, we summarize the current knowledge of ferroptosis, in terms of discovery, history, characteristics, mechanism, and the factors regulating liver diseases. We discuss how these factors and signaling pathways change in the context of liver disease. Furthermore, we focus on delineating the roles of effective therapeutic drugs or compounds in liver disease. In summary, we discuss the role of ferroptosis in liver disease, providing a strategy and new ideas for preventing liver disease, finding new therapeutic targets, and reducing liver damage.

Nuclear Factor Erythroid 2-Related Factor 2 in Regulating Cancer Metabolism

Significance: Nuclear factor erythroid 2 (NFE2)-related factor 2 (NFE2L2, or NRF2) is a transcription factor predominantly affecting the expression of antioxidant genes. NRF2 plays a significant role in the control of redox balance, which is crucial in cancer cells. NRF2 activation regulates numerous cancer hallmarks, including metabolism, cancer stem cell characteristics, tumor aggressiveness, invasion, and metastasis formation. We review the molecular characteristics of the NRF2 pathway and discuss its interactions with the cancer hallmarks previously listed. Recent Advances: The noncanonical activation of NRF2 was recently discovered, and members of this pathway are involved in carcinogenesis. Further, cancer-related changes (e.g., metabolic flexibility) that support cancer progression were found to be redox- and NRF2 dependent. Critical Issues: NRF2 undergoes Janus-faced behavior in cancers. The pro- or antineoplastic effects of NRF2 are context dependent and essentially based on the specific molecular characteristics of the cancer in question. Therefore, systematic investigation of NRF2 signaling is necessary to clarify its role in cancer etiology. The biggest challenge in the NRF2 field is to determine which cancers can be targeted for better clinical outcomes. Further, large-scale genomic and transcriptomic studies are missing to correlate the clinical outcome with the activity of the NRF2 system. Future Directions: To exploit NRF2 in a clinical setting in the future, the druggable members of the NRF2 pathway should be identified. In addition, it will be important to study how the modulation of the NRF2 system interferes with cytostatic drugs and their combinations.

SLC7A11/xCT in cancer: biological functions and therapeutic implications

Amino acid transporters mediate substrates across cellular membranes and their fine-tuned regulations are critical to cellular metabolism, growth, and death. As the functional component of system Xc-, which imports extracellular cystine with intracellular glutamate release at a ratio of 1:1, SLC7A11 has diverse functional roles in regulating many pathophysiological processes such as cellular redox homeostasis, ferroptosis, and drug resistance in cancer. Notably, accumulated evidence demonstrated that SLC7A11 is overexpressed in many types of cancers and is associated with patients' poor prognosis. As a result, SLC7A11 becomes a new potential target for cancer therapy. In this review, we first briefly introduce the structure and function of SLC7A11, then discuss its pathological role in cancer. We next summarize current available data of how SLC7A11 is subjected to fine regulations at multiple levels. We further describe the potential inhibitors of the SLC7A11 and their roles in human cancer cells. Finally, we propose novel insights for future perspectives on the modulation of SLC7A11, as well as possible targeted strategies for SLC7A11-based anti-cancer therapies.

Cystine transporter SLC7A11/xCT in cancer: ferroptosis, nutrient dependency, and cancer therapy

The cystine/glutamate antiporter SLC7A11 (also commonly known as xCT) functions to import cystine for glutathione biosynthesis and antioxidant defense and is overexpressed in multiple human cancers. Recent studies revealed that SLC7A11 overexpression promotes tumor growth partly through suppressing ferroptosis, a form of regulated cell death induced by excessive lipid peroxidation. However, cancer cells with high expression of SLC7A11 (SLC7A11^high) also have to endure the significant cost associated with SLC7A11-mediated metabolic reprogramming, leading to glucose- and glutamine-dependency in SLC7A11^high cancer cells, which presents potential metabolic vulnerabilities for therapeutic targeting in SLC7A11^high cancer. In this review, we summarize diverse regulatory mechanisms of SLC7A11 in cancer, discuss ferroptosis-dependent and -independent functions of SLC7A11 in promoting tumor development, explore the mechanistic basis of SLC7A11-induced nutrient dependency in cancer cells, and conceptualize therapeutic strategies to target SLC7A11 in cancer treatment. This review will provide the foundation for further understanding SLC7A11 in ferroptosis, nutrient dependency, and tumor biology and for developing novel effective cancer therapies.

Emerging mechanisms and applications of ferroptosis in the treatment of resistant cancers

The development of chemotherapy drugs has promoted anticancer treatment, but the effect on tumours is not clear because of treatment resistance; thus, it is necessary to further understand the mechanism of cell death to explore new therapeutic targets. As a new type of programmed cell death, ferroptosis is increasingly being targeted in the treatment of many cancers with clinical drugs and experimental compounds. Ferroptosis is stimulated in tumours with inherently high levels of ferrous ions by a reaction with abundant polyunsaturated fatty acids and the inhibition of antioxidant enzymes, which can overcome treatment resistance in cancers mainly through GPX4. In this review, we focus on the intrinsic cellular regulators against ferroptosis in cancer resistance, such as GPX4, NRF2 and the thioredoxin system. We summarize the application of novel compounds and drugs to circumvent treatment resistance. We also introduce the application of nanoparticles for the treatment of resistant cancers. In conclusion, targeting ferroptosis represents a considerable strategy for resistant cancer treatment.

Molecular characteristics associated with ferroptosis in hepatocellular carcinoma progression

The aim of this study was to investigate the genes associated with ferroptosis and the progression of hepatocellular carcinoma (HCC). The RNA sequencing data of erastin-induced ferroptosis in HCC cells were downloaded from the Sequence Read Archive database with accession number SRP119173. The microarray dataset GSE89377 of HCC progression was downloaded from the Gene Expression Omnibus database. The ferroptosis-related genes were screened by differential analysis and HCC progression-related genes were screened by cluster analysis using Mfuzz. Then, the genes associated with ferroptosis and HCC progression were screened by Venn analysis, followed by functional enrichment, protein-protein interaction (PPI) analysis, and transcription factor (TF) prediction. Finally, survival analysis was performed using data from the Cancer Genome Atlas database. A total of 33 upregulated and 52 downregulated genes associated with HCC progression and ferroptosis were obtained, and these genes were significantly involved in the negative regulation of ERK1 and ERK2 cascades; the NAD biosynthetic process; alanine, aspartate, and glutamate metabolism; and other pathways. The PPI network contained 52 genes and 78 interactions, of which, cell division cycle 20 (CDC20) and heat shock protein family B (small) member 1 (HSPB1) were hub genes found in higher degrees. Among the 85 genes associated with HCC progression and ferroptosis, two TFs (activating TF 3 (ATF3) and HLF) were predicted, with HSPB1 targeted by ATF3. In addition, 26 genes that were found to be significantly correlated with the overall survival of HCC patients were screened, including CDC20 and thyroid hormone receptor interactor 13. Several genes associated with HCC progression and ferroptosis were screened based on a comprehensive bioinformatics analysis. These genes played roles in HCC progression and ferroptosis via the negative regulation of the ERK1 and ERK2 cascades; the NAD biosynthetic process; and alanine, aspartate, and glutamate metabolism. ATF3 and HSPB1 played important roles in HCC progression and ferroptosis, with HSPB1 possibly regulated by ATF3.

Insight Into the Role of Ferroptosis in Non-neoplastic Neurological Diseases

Ferroptosis is an iron-dependent form of cell death characterized by the accumulation of intracellular lipid reactive oxygen species (ROS). Ferroptosis is significantly different from other types of cell death including apoptosis, autophagy, and necrosis, both in morphology and biochemical characteristics. The mechanisms that are associated with ferroptosis include iron metabolism, lipid oxidation, and other pathophysiological changes. Ferroptosis inducers or inhibitors can influence its occurrence through different pathways. Ferroptosis was initially discovered in tumors, though recent studies have confirmed that it is also closely related to a variety of neurological diseases including neurodegenerative disease [Alzheimer’s disease (AD), Parkinson’s disease (PD), etc.] and stroke. This article reviews the definition and characteristics of ferroptosis, the potential mechanisms associated with its development, inducers/inhibitors, and its role in non-neoplastic neurological diseases. We hope to provide a theoretical basis and novel treatment strategies for the treatment of central nervous system diseases by targeting ferroptosis.

Nrf2 and Ferroptosis: A New Research Direction for Neurodegenerative Diseases

Ferroptosis is a kind of regulated cell death (RCD) caused by the redox state disorder of intracellular microenvironment controlled by glutathione (GSH) peroxidase 4 (GPX4), which is inhibited by iron chelators and lipophilic antioxidants. In addition to classical regulatory mechanisms, new regulatory factors for ferroptosis have been discovered in recent years, such as the P53 pathway, the activating transcription factor (ATF)3/4 pathway, Beclin 1 (BECN1) pathway, and some non-coding RNA. Ferroptosis is closely related to cancer treatment, neurodegenerative diseases, ischemia–reperfusion of organ, neurotoxicity, and others, in particular, in the field of neurodegenerative diseases treatment has aroused people’s interest. The nuclear factor E2 related factor 2 (Nrf2/NFE2L2) has been proved to play a key role in neurodegenerative disease treatment and ferroptosis regulation. Ferroptosis promotes the progression of neurodegenerative diseases, while the expression of Nrf2 and its target genes (Ho-1, Nqo-1, and Trx) has been declined with aging; therefore, there is still insufficient evidence for ferroptosis and Nrf2 regulatory networks in the field of neurodegenerative diseases. In this review, we will provide a brief overview of ferroptosis regulatory mechanisms, as well as an emphasis on the mechanism of Nrf2 regulating ferroptosis. We also highlight the role of ferroptosis and Nrf2 during the process of neurodegenerative diseases and investigate a theoretical basis for further research on the relationship between Nrf2 and ferroptosis in the process of neurodegenerative diseases treatment.

Transcription factors in ferroptotic cell death

Ferroptosis, a form of regulated cell death, is characterized by an excessive degree of iron accumulation and lipid peroxidation. Although it was originally identified only in cells expressing a mutant RAS oncogene, ferroptosis has also been found in normal cells following treatment by small molecules (e.g., erastin and RSL3) or drugs (e.g., sulfasalazine, sorafenib, and artesunate), which target antioxidant enzyme systems, especially the amino acid antiporter system x_c^- and the glutathione peroxidase GPX4. Dysfunctional ferroptosis is implicated in various physiological and pathological processes (e.g., metabolism, differentiation, and immunity). Targeting the ferroptotic network appears to a new treatment option for diseases or pathological conditions (e.g., cancer, neurodegeneration, and ischemia reperfusion injury). While the molecular machinery of ferroptosis remains largely unknown, several transcription factors (e.g., TP53, NFE2L2/NRF2, ATF3, ATF4, YAP1, TAZ, TFAP2C, SP1, HIF1A, EPAS1/HIF2A, BACH1, TFEB, JUN, HIC1, and HNF4A) play multiple roles in shaping ferroptosis sensitivity through either transcription-dependent or transcription-independent mechanisms. In this review, we summarize recent progress in understanding the transcriptional regulation underlying ferroptotic cell death, and discuss how it has provided new insights into cancer therapy.

The epigenetic regulators and metabolic changes in ferroptosis-associated cancer progression

Ferroptosis, a novel form of regulated cell death, is different from other types of cell death in morphology, genetics and biochemistry. Increasing evidence indicates that ferroptosis has significant implications on cell death linked to cardiomyopathy, tumorigenesis, and cerebral hemorrhage to name a few. Here we summarize current literature on ferroptosis, including organelle dysfunction, signaling transduction pathways, metabolic reprogramming and epigenetic regulators in cancer progression. With regard to organelles, mitochondria-induced cysteine starvation, endoplasmic reticulum-related oxidative stress, lysosome dysfunction and golgi stress-related lipid peroxidation all contribute to induction of ferroptosis. Understanding the underlying mechanism in ferroptosis could provide insight into the treatment of various intractable diseases including cancers.

ACSL4 suppresses glioma cells proliferation via activating ferroptosis

Acyl-CoA synthetase long-chain family member 4 (ACSL4) is a member of the long chain family of acyl-CoA synthetase proteins, which have recently been shown to serve an important role in ferroptosis. Previous studies have suggested that ferroptosis is involved in the occurrence of glioma; however, the role of ACSL4 in glioma remains unknown. In the present study, a reduction of ferroptosis in human glioma tissues and glioma cells was observed. Subsequently, it was demonstrated that the expression of ACSL4 was also downregulated in human glioma tissues and cells. A ferroptosis inhibitor and inducer were used to investigate the effects of ferroptosis on viability. The results showed that promoting ferroptosis inhibited the proliferation of glioma cells, and that the use of inducers had the reverse effect. Therefore, it was hypothesized that the reduction in ACSL4 expression may have been involved in ferroptosis and proliferation in glioma. Overexpression of ACSL4 decreased expression of glutathione peroxidase 4 and increased the levels of ferroptotic markers, including 5-hydroxyeicosatetraenoic (HETE), 12-HETE and 15-HETE. Additionally, ACSL4 overexpression resulted in an increase in lactate dehydrogenase release and a reduction in cell viability. The opposite results were observed when ACSL4 was silenced. These findings suggest that ACSL4 regulates ferroptosis and proliferation of glioma cells. To further investigate the mechanism underlying ACSL4-mediated regulation of proliferation in glioma cells, cells were treated with small interfering (si)-ACSL4 and sorafenib, a ferroptosis inducer. sorafenib attenuated the ability of siRNA-mediated silencing of ACSL4, thus improving cell viability. These results demonstrate that ACSL4 protects glioma cells and exerts anti-proliferative effects by activating a ferroptosis pathway and highlight the pivotal role of ferroptosis regulation by ACSL4 in its protective effects on glioma. Therefore, ACSL4 may serve as a novel therapeutic target for the treatment of glioma.

Pannexin 1 mediates ferroptosis that contributes to renal ischemia/reperfusion injury

Renal ischemia/reperfusion injury (IRI) is a significant challenge in perioperative medicine and is related to oxidative programmed cell death. However, the role of ferroptosis, a newly discovered form of oxidative cell death, has not been evaluated widely. Pannexin 1 (PANX1), an ATP-releasing pathway family protein, has pro-apoptotic effects during kidney injury. Here, we demonstrate that PANX1 deletion protects against renal IRI by regulating ferroptotic cell death. Panx1 knockout mice subjected to renal IRI had decreased plasma creatinine, malondialdehyde (MDA) levels in kidney tissues, and tubular cell death (visible as decreased TUNEL-positive renal tubular cells) compared with WT mice. In cultured human kidney 2 (HK-2) cells, silenced Panx1 expression significantly attenuated ferroptotic lipid peroxidation and iron accumulation induced by the ferroptosis inducer erastin. Moreover, the Panx1 silencing significantly modulated ferroptosis-related protein expression. Furthermore, Panx1 deletion induced the expression of a cytoprotective chaperone, heme oxygenase-1 (HO-1), and inhibited ferroptinophagy via the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway. In summary, Panx1 deletion protects against renal IRI by attenuating MAPK/ERK activation in a ferroptotic pathway. Our findings provide critical insights into the role of PANX1 in ferroptotic cell death and highlight a potential therapeutic target for the management of acute kidney injury (AKI) during the perioperative period.